With rapid development of Internet services and multimedia services, higher requirements are imposed on a capacity and usage of an optical communications network. Featuring high frequency band usage and flexibility, an ultra dense wavelength-division multiplexing (UDWDM) technology with a frequency separation less than 10 GHz has a great use value in a transmission network in the future.
A UDWDM convergence networking mode meets a high-capacity transmission requirement in the future and allows access by means of direct coupling, and does not require convergence and filtering for multiple times, so that operation device costs can be reduced, and operation efficiency can be improved.
Specifically, an optical communications network obtained in the UDWDM convergence networking mode includes one primary node and at least one access node. In an uplink, access nodes separately use different UDWDM frequency bands, uplink signals of the access nodes are combined by using a coupler in a communications link, and a combined uplink signal is sent to the primary node. In a downlink, the primary node sends a downlink signal to nodes in a broadcast mode. In the downlink, for the downlink signal broadcast by the primary node, a frequency division multiplexing manner may be used, so that the access nodes receive the downlink signal in different frequency bands; or a time division multiplexing manner may be used, so that the access nodes receive the downlink signal in different timeslots.
However, in actual application, the access nodes may use different laser light sources, and a center frequency offset of a laser light source may be +/−5 GHz. Therefore, in an uplink process, uplink signals sent by the access nodes cause crosstalk between adjacent channels, and consequently, transmission of the uplink signals is affected.